Morphological variability of the extensor hallucis longus in human fetuses

Area of Science:

• Anatomy
• Embryology
• Orthopedics

Background:

• The extensor hallucis longus (EHL) tendon originates from the fibula and inserts into the great toe's distal phalanx.
• Understanding EHL tendon insertion is vital for foot biomechanics and surgical procedures.

Purpose of the Study:

• To classify the insertion patterns of the extensor hallucis longus tendon in human fetuses.
• To establish a foundational classification for EHL tendon variations.

Main Methods:

• Examination of 100 lower limbs from 50 human fetuses (18-38 weeks gestation).
• Dissection and morphological analysis of the extensor hallucis longus tendon insertion.

Main Results:

• A three-type classification of EHL tendon insertion was established.
• Type I (68%) featured a single tendon inserting into the distal phalanx base.
• Type II (27%) showed a dual insertion, with an auxiliary tendon to the proximal phalanx.
• Type III (5%) involved a dual insertion, with the auxiliary tendon connecting to the extensor hallucis brevis tendon.

Conclusions:

• The extensor hallucis longus tendon exhibits considerable variability in its insertion approach in fetal development.
• This initial classification provides a basis for understanding anatomical variations in the EHL tendon.